The head of the BBC accused Iran of intimidating staff members of its Persian service through slander, snooping and the arrest of their relatives, AP reported.

BBC director-general Mark Thompson said “a campaign of bullying and harassment” against the broadcaster had worsened in recent months.

Thompson said in a blog post that last week the sister of a BBC Persian staff member was detained and held in solitary confinement in a Tehran prison. She has since been released. He said it was one of several occasions on which employees’ relatives have been detained and “urged to get their relatives in London to either stop working for the BBC, or to ‘cooperate’ with Iranian intelligence officials.”

Thompson said staff members’ email and Facebook accounts had been hacked, and they had faced false accusations of sexual assault, drug trafficking and financial crimes in official Iranian media outlets.

Britain’s Middle East minister, Alistair Burt, said Iranian officials’ ”deplorable tactics illustrate again the deteriorating human rights situation in Iran, and the desperation of the Iranian regime to silence any independent voices.”

Diplomatic relations between Britain and Iran have deteriorated as tensions mount over Tehran’s disputed nuclear program.

Britain downgraded ties with Iran following a major attack on its embassy in Tehran in November, which it insists was sanctioned by the Islamic republic’s ruling elite.

New York-based Human Rights Watch said Iran’s harassment was part of a wave of arrests against journalists and bloggers ahead of parliamentary elections scheduled for next month.